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produce a small height SSD. That is, the raw range of heights does not necessarily reflect the <br />character of the vegetation. <br />If the height SSD is large then that indicates plant heights vary al] up and down the scale, <br />with no particular height being common. But if it is small then that indicates most plants aze pretty <br />close to the same height with only a few or no plants varying far from the mean. <br />In general, very eazly in the development of the vegetation the height SSD can be very small <br />as al] the plants are seedlings of more or less the same size. This would be indicated as well in a <br />narrow maximum-minimum range. But with somewhat more development the height SSD can <br />become very large as plant heights vary tremendously. This would also be reflected in a lazge range <br />between the shortest and the tallest plants. Sometimes, in these instances, the statistically calculated <br />height SSD range (mean height plus height SSD versus mean height minus height SSD) can result in <br />the bottom of the range actually being a negative height. Of course, it is not possible for a plant to <br />have a negative height (height less than zero), but it demonstrates just how much variation is present <br />in a population of a single species with widely varying plant sizes. With increased maturity the <br />height SSD value should become smaller, unless there are a lot of more mature trees and a fresh <br />invasion of lots of young plants. In that case, the height SSD can become large again. <br />In a few of the transects sampled here, the maximum and minimum height range is quite <br />large, but the height SSD is small. When this occurs the height SSD is saying that most of the plants <br />are more or less the same size, but there are a few rather tall and a few rather short plants. In other <br />words, even though the absolute plant height range is great, the few plants that are very tall or very <br />short don't really count much in defining the overall character of the vegetation. <br />EXCLOSUREI- <br />Genera[ Description for 2007: This exclosure is located on the west side of the last azea <br />to be mined north of the road crossing. The exclosure is long and narrow paralleling the currently <br />indefinite stream channel through this azea. The exclosure can be divided into three rather vague <br />zones. The most northerly third is the wettest and has dense growths of baltic rush (Juncus balticus) <br />as well as other wetland species. Woody growth here is mostly willow with only a little cottonwood, <br />mainly azound the edges in drier soils, but cottonwood increased in 2007. The southem third is the <br />driest area where willow density declined markedly in 2006 but increased in 2007 and cottonwood <br />increased both in density and height. The middle third is more or less a blend of the wet northern <br />areas and the drier southern aeeas. A lazge, but old and declining cottonwood forest exists to the west <br />of the exclosure at a higher elevation. There is some evidence of root sprouting on the bank leading <br />down into the stream comdor. <br />Throughout the exclosure are variously sized, slightly elevated, dry, sandy mounds where <br />there currently is little woody growth but baltic rush projects up through the sand. In 2007 woody <br />2007 Annual Report Coal Creek Wetland Mitigation Permit DA 198811488 Page 7 <br />